XSLT performance issue with large data - xslt

Question

having performance issues with my xslt code:
this is my input file:
<?xml version="1.0" encoding="UTF-8"?>
<Products>
<Product ID="111111" Type="Item" ParentID="7402">
<Name>ABC</Name>
<Values>
<Value AttributeID="11">8.00</Value>
<Value AttributeID="12">8.00</Value>
<Value AttributeID="13">0.18</Value>
</Values>
<Product ID="B582B65D" Type="UID" ParentID="111111">
<Values>
<Value AttributeID="11">8.00</Value>
<Value AttributeID="12">8.00</Value>
<Value AttributeID="13">0.18</Value>
<Value AttributeID="14">0.18</Value>
</Values>
</Product>
</Product>
<Product ID="222222" Type="Item" ParentID="7402">
<Name>XYZ</Name>
<Values>
<Value AttributeID="12">8.00</Value>
<Value AttributeID="13">8.00</Value>
<Value AttributeID="15">0.18</Value>
</Values>
<Product ID="B582B65D" Type="UID" ParentID="111111">
<Values>
<Value AttributeID="11">8.00</Value>
<Value AttributeID="12">8.00</Value>
<Value AttributeID="16">0.18</Value>
<Value AttributeID="18">0.18</Value>
</Values>
</Product>
</Product>
</Products>
and this is my transformation code:
<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:math="http://exslt.org/math"
extension-element-prefixes="math">
<xsl:output method="xml" indent="yes" />
<xsl:param name="file2" select="document('Mapping.xml')" />
<xsl:template match="/Products">
<Products>
<xsl:for-each select="Product">
<xsl:call-template name="item" />
</xsl:for-each>
</Products>
</xsl:template>
<xsl:template name="item">
<Product type="{./#Type}" ID="{./#ID}">
<xsl:for-each select="./Values/Value">
<xsl:variable name="Idval" select="#AttributeID" />
<xsl:element name="{$file2//Groups/AttributeID[#ID=$Idval]/#group}">
<xsl:element name="{$file2//Groups/AttributeID[#ID=$Idval]}">
<xsl:attribute name="ID"><xsl:value-of select="$Idval"/></xsl:attribute>
<xsl:value-of select="." />
</xsl:element>
</xsl:element>
</xsl:for-each>
<xsl:call-template name="uid" />
</Product>
</xsl:template>
<xsl:template name="uid">
<Product type="{./Product/#Type}" ParentId="{./Product/#ParentID}">
<xsl:for-each select="./Product/Values/Value">
<xsl:variable name="Idval" select="#AttributeID" />
<xsl:element name="{$file2//Groups/AttributeID[#ID=$Idval]/#group}">
<xsl:element name="{$file2//Groups/AttributeID[#ID=$Idval]}">
<xsl:attribute name="ID"><xsl:value-of select="$Idval"/></xsl:attribute>
<xsl:value-of select="." />
</xsl:element>
</xsl:element>
</xsl:for-each>
</Product>
</xsl:template>
</xsl:stylesheet>
above xslt is using below xml file for mapping attribute id to corresponding name and group
Mapping.xml
<?xml version="1.0" encoding="UTF-8"?>
<Groups>
<AttributeID ID="11" group="Pack1">Height</AttributeID>
<AttributeID ID="12" group="Pack2">Width</AttributeID>
<AttributeID ID="13" group="Pack1">Depth</AttributeID>
<AttributeID ID="14" group="Pack3">Length</AttributeID>
<AttributeID ID="15" group="Pack3">Lbs</AttributeID>
<AttributeID ID="16" group="Pack4">Litre</AttributeID>
</Groups>

Answer 1

Replace the use of expressions like
select="$file2//Groups/AttributeID[#ID=$Idval]"
with a key:
<xsl:key name="ID" match="Groups/AttributeID" use="#ID"/>
and then
select="key('ID', $IDval, $file)"/>
Alternatively, Saxon-EE will do this optimization for you automatically.
The key() function with 3 arguments is XSLT 2.0 syntax. If you have the misfortune to be using XSLT 1.0, you have to write a dummy xsl:for-each that makes $file the context item, because key() will only select within the document containing the context item.

Answer 2

Define a key for the cross document lookup: <xsl:key name="by-id" match="Groups/AttributeID" use="#ID"/>, then (assuming an XSLT 2.0 processor) you can simplify expressions like <xsl:element name="{$file2//Groups/AttributeID[#ID=$Idval]/#group}"> to <xsl:element name="{key('by-id', #AttributeID, $file2)/#group">. Make the same change for the other cross references you have, i.e. all those $file2//Groups/AttributeID[#ID=$Idval] expressions should use the key lookup.

Answer 3

Making the simplified assumption that your second file isn't too big, you want to fold the values there into your template. It would work with XSLT 1.0 too. Something like this:
<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:math="http://exslt.org/math"
extension-element-prefixes="math">
<xsl:output method="xml" indent="yes" />
<xsl:template match="/">
<Products>
<xsl:apply-templates select="/Products/Product" />
</Products>
</xsl:template>
<xsl:template match="Product">
<xsl:element name="Product">
<xsl:apply-templates select="#*" />
<xsl:apply-templates />
</xsl:element>
</xsl:template>
<xsl:template match="Name">
<Name>
<xsl:value-of select="." />
</Name>
</xsl:template>
<xsl:template match="#*">
<xsl:attribute name="{name()}">
<xsl:value-of select="." />
</xsl:attribute>
</xsl:template>
<xsl:template match="Values">
<Values>
<xsl:apply-templates />
</Values>
</xsl:template>
<!-- Templates for individual AttributeIDs, only when there are few -->
<xsl:template match="Value[#AttributeID='11']">
<Pack1>
<xsl:element name="Height">
<xsl:attribute name="ID">
<xsl:value-of select="#AttributeID" />
</xsl:attribute>
<xsl:value-of select="." />
</xsl:element>
</Pack1>
</xsl:template>
<!-- Repeat for the other AttributeID values -->
</xsl:stylesheet>
(Typed off my head, will contain typos)
Of course if it is big Michael's advice is the best course of action.